基于多模式协同的移动终端天线关键技术研究

The rapid development of mobile communication drives the continuous innovation of antenna technology. The requirement of high-speed wireless transmission rate and the limitation of mobile terminal volume pose great challenge to the design of mobile terminal antenna. In this project, the method of improving the performances of mobile terminal antenna is studied from two aspects: increasing antenna bandwidth and the number of antennas. Based on mode theory, the eigen-mode distribution of mobile terminal without excitation is analyzed in the whole frequency band firstly. Then, the feed source is designed and added to make multiple modes work together. The applications of multi-mode synergy are mainly in two aspects, namely multi-mode coupling and multi-mode orthogonality. For multi-mode coupling, this project will study the mode combination of asymmetric ground plane and feed monopole to increase the bandwidth. This combination is not only helpful for miniaturization and integration, but also flexible in mode tuning. For multi-mode orthogonality, this project will use the eigen-mode theory to design a wideband MIMO antenna in high frequency band. This design is expected to achieve high isolation in broad band by combining the eigen-modes of metal frame and ground plane. In addition, in order to further extend the bandwidth of the MIMO antenna, this project will adopt the techniques of virtual-short circuit and lumped components loading to move the resonant frequency of specific mode.

移动通信的飞速发展驱动着天线技术的不断创新。高速无线传输速率的需求与移动终端空间严格受限的特点对移动终端天线的设计提出了巨大挑战。本项目将从增加天线带宽与数量这两方面研究改善移动终端天线性能的方法。项目以移动终端天线的模式为切入点，先从无源的角度分析移动终端在全频段的本征模式分布。在此基础上研究馈源的添加与设计，以实现多个模式的协同工作。多模式协同工作主要体现在多模式耦合与多模式正交这两方面。针对多模式耦合，本项目拟研究不对称地板与单极子馈源的模式组合来扩展天线的带宽。这种组合不仅可实现平面小型化集成，而且模式调节也较灵活。针对多模式正交，本项目拟用本征模理论研制移动通信高频段的宽带MIMO天线。通过有机结合金属中框与手机地板的本征模，该设计可望在宽带范围内实现高隔离。此外，为了进一步扩展MIMO天线的带宽，本项目拟采用虚拟短路和集总元件加载等技术实现特定模式的谐振频率的搬移。

项目按照预定方案，系统研究了适用于4G/5G移动终端的单天线和多天线技术。项目以天线的模式为切入点，借助本征模理论，先从无源的角度研究了移动终端在全频段内的本征模式分布，之后研究了单馈源与多馈源的添加，实现了多个模式的协同工作。具体的研究工作和成果包括：1）利用本征模理论分析了金属边框与手机地板在宽频段内的本征模式，通过添加合适的激励以及电感调谐，去除了传统的谐振式馈源，地板与边框之间的净空仅为2mm，带宽覆盖了824-960MHz频段和1710-2690MHz频段，整个频段的辐射效率均在60%以上；2）为了满足5G多天线的需求，项目研制了一系列工作在Sub-6GHz频段的5G移动终端MIMO天线。通过集总电感电容解耦，首次实现了四个天线单元的聚合，单元间距仅为1mm，在3400-3600MHz频段的端口隔离优于10dB；3）研制了一款低成本毫米波波束扫描5G终端天线。通过在串行传输线周期性的添加二极管开关，构造了具有2比特精度的新型移相器，无需传统的功分器和移相器，阵列实现了112°的波束扫描范围。